Sealing Between Alignable Windows for Lateral Wellbore Drilling

ABSTRACT

Sealing may be provided between alignable windows for lateral wellbore drilling. A method for use with a lateral wellbore includes the steps of: positioning a swellable seal material between a closure device and a housing of a window assembly; swelling the seal material to thereby prevent fluid transfer through a window formed in a sidewall of the housing; and then installing the window assembly in a parent wellbore. A lateral wellbore system includes a window assembly with a window formed through a sidewall of a generally tubular housing, and a swollen seal material preventing fluid transfer through the window. A window assembly includes a generally tubular housing having a window formed through a sidewall of the housing, a closure device having another window formed through a wall of the closure device; and a swellable seal material which prevents fluid transfer between the windows.

BACKGROUND

The present disclosure relates generally to equipment utilized and operations performed in conjunction with subterranean wells and, in an embodiment described herein, more particularly provides for sealing between alignable windows for lateral wellbore drilling.

When a lateral or branch wellbore is drilled from a main or parent wellbore, it is common practice to mill a window through the sidewall of a casing or liner string in the parent wellbore in order to initiate the lateral wellbore drilling process. However, the milling process is very time consuming and expensive, and entails certain risks.

Alternatively, the casing string could be provided with a window pre-milled in its sidewall, with an easily drilled through material (such as composite or aluminum, etc.) temporarily closing off the window for circulating and cementing purposes. However, such easily drilled through material is also relatively weak as compared to the casing string, unless the material is made very thick, which presents certain problems in the restricted confines of a wellbore.

Another alternative is the use of an inner sleeve in the casing string to temporarily close off a pre-milled window. The inner sleeve could be displaced to uncover the pre-milled window but, due to the complex geometry between the casing string and the inner sleeve, obtaining a seal to prevent fluid transfer through the window during circulating and cementing would be very difficult.

Therefore, it will be appreciated that improvements are needed in the art of providing windows for lateral wellbore drilling.

SUMMARY

In the present specification, lateral wellbore window methods and systems are provided which solve at least one problem in the art. One example is described below in which a swellable seal is used between alignable windows to thereby prevent fluid transfer between the windows during operations such as circulating and cementing. Another example is described below in which a window which has been previously sealed using a swollen seal material is then opened to permit drilling and/or accessing a lateral wellbore through the window.

In one aspect, a lateral wellbore system includes a window assembly with a window formed through a sidewall of a generally tubular housing. A swollen seal material prevents fluid transfer through the window.

In another aspect, a method for use with a lateral wellbore includes the steps of: positioning a swellable seal material between a closure device and a housing of a window assembly; swelling the seal material to thereby prevent fluid transfer through a window formed in a sidewall of the housing; and then installing the window assembly in a parent wellbore.

In yet another aspect, a window assembly for use in a subterranean well includes a generally tubular housing having a window formed through a sidewall of the housing, and a closure device having another window formed through a wall of the closure device. A swellable seal material prevents fluid transfer between the windows.

These and other features, advantages, benefits and objects will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of representative embodiments hereinbelow and the accompanying drawings, in which similar elements are indicated in the various figures using the same reference numbers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a lateral wellbore drilling system and associated method which embody principles of the present disclosure;

FIG. 2 is an enlarged scale schematic cross-sectional view of a lateral wellbore window assembly usable in the system of FIG. 1;

FIG. 3 is a schematic partially cross-sectional view of a method of operating the window assembly of FIG. 2;

FIG. 4 is a schematic cross-sectional view of the window assembly in a closed configuration, taken along line 4-4 of FIG. 2;

FIG. 5 is a schematic cross-sectional view of the window assembly in an open configuration;

FIG. 6 is an enlarged scale schematic detail of the window assembly of FIG. 4; and

FIG. 7 is a schematic cross-sectional view of an alternate construction of the window assembly.

DETAILED DESCRIPTION

It is to be understood that the various embodiments described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of the present disclosure. The embodiments are described merely as examples of useful applications of the principles of the disclosure, which are not limited to any specific details of these embodiments.

In the following description of the representative embodiments of the disclosure, directional terms, such as “above”, “below”, “upper”, “lower”, etc., are used for convenience in referring to the accompanying drawings. In general, “above”, “upper”, “upward” and similar terms refer to a direction toward the earth's surface along a wellbore, and “below”, “lower”, “downward” and similar terms refer to a direction away from the earth's surface along the wellbore.

Representatively illustrated in FIG. 1 is a lateral wellbore drilling system 10 and associated method which embody principles of the present disclosure. In the method, a parent wellbore 12 is drilled, and then a lateral wellbore 14 is drilled extending outwardly from the parent wellbore.

In order to facilitate drilling of the lateral wellbore 14, the system 10 includes a window assembly 16 interconnected as part of a casing string 18 installed in the parent wellbore 12. As used herein, the term “casing string” is used to indicate a generally tubular string used to provide a protective lining for a wellbore, and can include at least those types of strings known as casing and liner strings, which may be made of any type of material (such as steel, other metals and alloys, plastics, composite materials, etc.).

The window assembly 16 can include various features, such as an azimuthally orienting latch profile 20, and other features not specifically illustrated in the drawings. The latch profile 20 could be, for example, a Latch Coupling of the type available from Sperry Drilling Services, and may be used to secure and orient equipment such as a drilling whipstock (not shown) for drilling the lateral wellbore 14.

As depicted in FIG. 1, the window assembly 16 also includes a generally tubular housing 22 and a closure device 24. The closure device 24 is used to initially close off a window 26 formed through a sidewall of the housing 22.

When it is desired to drill (or otherwise obtain access to) the lateral wellbore 14 from the parent wellbore 12, the closure device 24 is displaced relative to the housing 22. In the example illustrated in FIG. 1, this displacement results in alignment of the window 26 in the housing 22 with another window 28 formed through the closure device 24.

Preferably, the closure device 24 prevents fluid transfer through the window 26 in the housing 22 while the casing string 18 is being installed in the parent wellbore 12, during fluid circulation through the casing string, and during cementing of the casing string in the parent wellbore. After the cementing operation, the closure device 24 is displaced to open the window 26 and thereby permit drilling the lateral wellbore 14.

Note, however, that the various method steps and elements of the system 10 described above and depicted in the drawings can be altered to suit the particular circumstances or desired outcome of an actual well operation. For example, it is possible that the lateral wellbore 14 could be drilled prior to installing the casing string 18 in the parent wellbore 12, it is not necessary for the closure device 24 to include the window 28 which is alignable with the window 26, it is not necessary for the casing string 18 to be cemented in the parent wellbore, the closure device is not necessarily internal to the housing 22, the closure device is not necessarily tubular in shape, the latch profile 20 could be positioned above the window 26, etc. Thus, it should be clearly understood that the principles of the present disclosure are not limited to the details of the system 10 and associated methods described herein.

Referring additionally now to FIG. 2, an enlarged scale cross-sectional view of the window assembly 16 is representatively illustrated. In this view, further details of the window assembly 16 may be seen.

Note that the windows 26, 28 are aligned with each other in the open configuration of the window assembly 16 depicted in FIG. 1, but the windows are not aligned with each other in the closed configuration of the window assembly depicted in FIG. 2. Thus, in the closed configuration, the closure device 24 prevents fluid transfer through the window 26, and in the open configuration, the closure device permits fluid transfer through the window 26.

In this example of the window assembly 16, the closure device 24 is rotated about a longitudinal axis 30 of the window assembly in order to displace the closure device between its open and closed positions. As described more fully below, the latch profile 20 and recesses 32 formed in the interior of the closure device 24 facilitate this rotation of the closure device, but other means may be used to displace the closure device if desired.

Preferably, the window assembly 16 is installed in the parent wellbore 12 with the closure device 24 in its closed position preventing fluid transfer through the window 26. In this manner, fluid may be circulated through the entire casing string 18 during its installation. Also, when the casing string 18 is properly positioned in the wellbore 12, it may be cemented in place by flowing the cement through the casing string and into the annulus between the casing string and the wellbore.

After the cementing operation, the closure device 24 is preferably displaced to its open position. With the windows 26, 28 aligned, the lateral wellbore 14 can be drilled through the windows (e.g., by installing a drilling whipstock in the window assembly 16 and deflecting a drill string from within the casing string 18 outward through the windows), access to the lateral wellbore is permitted, etc.

Referring additionally now to FIG. 3, a schematic partially cross-sectional view of the system 10 and associated method is representatively illustrated. In this view, one technique for rotating the closure device 24 between its open and closed positions is depicted.

A service-tool 34 is conveyed into the window assembly 16 on a tubular string 36. A latch 38 at a lower end of the service tool 34 engages the latch profile 20, thereby axially and azimuthally aligning the service tool with the window assembly 16. This alignment positions dogs or lugs 40 on the service tool 34 opposite the recesses 32 in the closure device 24 (see FIG. 2).

Pressure is applied to the tubular string 36 to cause the lugs 40 to extend outward into engagement with the recesses 32. The tubular string 36 and service tool 34 above the latch 38 are then rotated to thereby rotate the closure device 24. When the windows 26, 28 are properly aligned with each other, an indication of this alignment will be provided by, for example, an increased torque in the tubular string 36 and/or the service tool 34 causing a release of pressure from the tubular string, etc.

When the applied pressure is released from the tubular string 36, the lugs 40 will withdraw from the recesses 32, and the service tool 34 can be retrieved from the well. Latches, snap rings, detents, etc. can be provided in the window assembly 16 to retain the closure device 24 in its open position.

Referring additionally now to FIG. 4, an enlarged scale cross-sectional view of the window assembly 16 is representatively illustrated, taken along line 4-4 of FIG. 2. In this view, the window assembly 16 is in its closed configuration, with the closure device 24 preventing fluid transfer through the window 26.

Referring additionally now to FIG. 5, the window assembly 16 is depicted in its open configuration, with the windows 26, 28 aligned and permitting fluid transfer through the windows between the interior and exterior of the window assembly. Note that the closure device 24 is rotated 180 degrees about the longitudinal axis 30 of the window assembly 16 between its closed and open positions. Of course, depending on the geometry of the window assembly 16, other amounts of rotation of the closure device 24 may be used if desired.

In one unique aspect of the window assembly 16, a swellable seal material 42 is positioned in the annular space between the closure device 24 and housing 22. The seal material 42 is also positioned in such a way as to prevent fluid transfer between the windows 26, 28 when the closure device 24 is in its closed position.

An enlarged scale detailed view of the seal material 42 between the housing 22 and closure device 24 is representatively illustrated in FIG. 6. In this view, it may be seen that the seal material 42 effectively closes off the annular space between the housing 22 and closure device 24.

In the illustrated example, the seal material 42 is a swellable material which swells in response to contact with a certain fluid. The term “swell” and similar terms (such as “swellable”) are used herein to indicate an increase in volume of a seal material. Typically, this increase in volume is due to incorporation of molecular components of the fluid into the seal material itself, but other swelling mechanisms or techniques may be used, if desired.

The seal material 42 is preferably adhered to an exterior surface of the closure device 24. When the seal material 42 swells in the window assembly 16, it preferably expands radially outward into contact with an inner surface of the housing 22. This swelling of the seal material 42 is preferably accomplished prior to installing the window assembly 16 in the wellbore 12.

Note that swelling is not the same as expanding, although a seal material may expand as a result of swelling. For example, in some conventional packers, a seal element may be expanded radially outward by longitudinally compressing the seal element, or by inflating the seal element. In each of these cases, the seal element is expanded without any increase in volume of the seal material of which the seal element is made. Thus, in these conventional packers, the seal element expands, but does not swell.

The fluid which causes swelling of the swellable material could be water and/or hydrocarbon fluid (such as oil or gas). The fluid could be a gel or a semi-solid material, such as a hydrocarbon-containing wax or paraffin which melts when exposed to increased temperature. The fluid could cause swelling of the swellable material due to passage of time.

Various swellable materials are known to those skilled in the art, which materials swell when contacted with water and/or hydrocarbon fluid, so a comprehensive list of these materials will not be presented here. Partial lists of swellable materials may be found in U.S. Pat. Nos. 3,385,367 and 7,059,415, and in U.S. Published Application No. 2004-0020662, the entire disclosures of which are incorporated herein by this reference.

The swellable material may have a considerable portion of cavities which are compressed or collapsed. When exposed to higher pressure, the material is expanded by the cavities filling with fluid.

This type of swellable material might be used where it is desired to expand the material in the presence of gas rather than oil or water. A suitable swellable material is described in International Application No. PCT/NO2005/000170 (published as WO 2005/116394), the entire disclosure of which is incorporated herein by this reference.

It should, thus, be clearly understood that any swellable material which swells when contacted by any type of fluid may be used in keeping with the principles of the invention. Preferably, the seal material 42 used in the window assembly 16 is swellable in response to contact with a hydrocarbon fluid.

It will be appreciated that, due to the complex geometry between the housing 22 and the closure device 24, it would be very difficult to use a conventional seal (such as an o-ring) to prevent fluid transfer between the windows 26, 28 in the closed configuration of the window assembly 16. In contrast, the swellable seal material 42 is able to conform to the complex geometry and any surface irregularities on the exterior surface of the closure device 24 and on the inner surface of the housing 22.

In addition, the seal material 42 can serve to centralize the closure device 24 within the housing 22. In one embodiment, the exterior surface of the closure device 24 may be completely covered with the seal material 42. In other embodiments, the seal material 42 could extend only about the window 26 when the closure device 24 is in its closed position. The seal material 42 may be shaped and positioned in various different ways in keeping with the principles of this disclosure.

Referring additionally now to FIG. 7, an alternate construction of the window assembly 16 is representatively illustrated. In this construction, the closure device 24 is displaced axially, instead of rotationally, to align the windows 26, 28.

As depicted in FIG. 7, the closure device 24 is in its closed position preventing fluid transfer through the window 26. However, when the closure device 24 is displaced downward relative to the housing 22 (e.g., in a direction parallel to the longitudinal axis 30 of the window assembly), the windows 26, 28 will be aligned, thereby permitting fluid transfer between the windows.

The swellable seal material 42 in the example of FIG. 7 extends completely around the closure device 24. The seal material 42 prevents fluid transfer between the windows 26, 28 when the closure device 24 is in its closed position

Note that it is not necessary for the closure device 24 to have a generally tubular shape, or for the window 28 to be formed through a wall of the closure device. For example, the closure device 24 could instead close off the window 26 without having a tubular shape, or the closure device could be a sleeve without a window in its sidewall (in which case the closure device would not cover or be positioned opposite the window 26 in the open position of the closure device).

Note, also, that any type of displacement may be used to move the closure device 24 between its closed and open positions (such as, axial, rotational, helical, reciprocal or any other displacement). The closure device 24 could be retrieved from within the housing 22, instead of remaining in the housing after the closure device is displaced to its open position. Thus, it should be clearly understood that the present disclosure is not limited to any of the particular details of the window assembly 16 described herein.

It may now be fully appreciated that the system 10, its associated methods and the window assembly 16 provide significant advances in the art of drilling lateral wellbores. Specifically, a window is provided in a casing string in a parent wellbore for drilling and accessing a lateral wellbore, without the need for milling through a sidewall of the casing string, but with enhanced sealing to permit circulation and cementing prior to opening the window, and in a manner which allows the window to be conveniently opened.

In particular, a lateral wellbore system 10 is provided which includes a window assembly 16 having a window 26 formed through a sidewall of a generally tubular housing 22, and with a swollen seal material 42 preventing fluid transfer through the window. The seal material 42 is preferably swollen prior to installation of the window assembly 16 in a wellbore 12.

The window assembly 16 may further include another window 28 formed through a sidewall of a closure device 24, and the seal material 42 may prevent fluid transfer between the windows 26, 28.

The window 28 may be displaceable into alignment with the window 26, thereby permitting drilling of a lateral wellbore 14 through the aligned windows 26, 28 The closure device 24 may be rotatable to align the windows 26, 28. The closure device 24 may be displaceable axially relative to the housing 22 to align the windows 26, 28.

The window assembly 16 may include the closure device 24 which is displaceable to open the window 26, with the seal material 42 sealing between the closure device 24 and the housing 22. The closure device 24 may be generally tubular in shape and may be received within an interior of the housing 22.

A method for use with a lateral wellbore 14 is provided which includes the steps of: positioning a swellable seal material 42 between a closure device 24 and a housing 22 of a window assembly 16; swelling the seal material 42 to thereby prevent fluid transfer through a window 26 formed in a sidewall of the housing 22; and then installing the window assembly 16 in a parent wellbore 12.

The method may also include the step of displacing the closure device 24 relative to the housing 22, thereby permitting fluid transfer through the window 26.

The displacing step may include rotating the closure device 24 relative to the housing 22. The displacing step may include axially displacing the closure device 24 relative to the housing 22.

The displacing step may include aligning the window 26 with another window 28 formed through the closure device 24. The method may include the step of drilling the lateral wellbore 14 through the aligned windows 26, 28. The swelling step may include preventing fluid transfer between the windows 26, 28.

The seal material swelling step may be performed only prior to the window assembly installing step.

Also provided by the present disclosure is a window assembly 16 for use in a subterranean well. The window assembly 16 includes a generally tubular housing 22 having a window 26 formed through a sidewall of the housing, a closure device 24 having another window 28 formed through a wall of the closure device, and a swellable seal material 42 which prevents fluid transfer between the windows 26, 28.

Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to these specific embodiments, and such changes are within the scope of the principles of the present disclosure. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims and their equivalents. 

1. A lateral wellbore system, comprising: a window assembly including a first window formed through a sidewall of a generally tubular housing, and a swollen seal material preventing fluid transfer through the first window.
 2. The system of claim 1, wherein the seal material is swollen prior to installation of the window assembly in a wellbore.
 3. The system of claim 1, wherein the window assembly further includes a second window formed through a wall of a closure device, and wherein the seal material prevents fluid transfer between the first and second windows.
 4. The system of claim 3, wherein the second window is displaceable into alignment with the first window, thereby permitting drilling of a lateral wellbore through the aligned first and second windows.
 5. The system of claim 3, wherein the closure device is rotatable to align the first and second windows.
 6. The system of claim 3, wherein the closure device is displaceable axially relative to the housing to align the first and second windows.
 7. The system of claim 1, wherein the window assembly further includes a closure device displaceable to open the first window, and wherein the seal material seals between the closure device and the housing.
 8. The system of claim 1, wherein the closure device is generally tubular in shape and is received within an interior of the housing.
 9. A method for use with a lateral wellbore, the method comprising the steps of: positioning a swellable seal material between a closure device and a housing of a window assembly; swelling the seal material to thereby prevent fluid transfer through a first window formed in a sidewall of the housing; and then installing the window assembly in a parent wellbore.
 10. The method of claim 9, further comprising the step of displacing the closure device relative to the housing, thereby permitting fluid transfer through the window.
 11. The method of claim 10, wherein the displacing step further comprises rotating the closure device relative to the housing.
 12. The method of claim 10, wherein the displacing step further comprises axially displacing the closure device relative to the housing.
 13. The method of claim 10, wherein the displacing step further comprises aligning the first window with a second window formed through the closure device.
 14. The method of claim 13, further comprising the step of drilling the lateral wellbore through the aligned first and second windows.
 15. The method of claim 13, wherein the swelling step further comprises preventing fluid transfer between the first and second windows.
 16. The method of claim 9, wherein the swelling step is performed only prior to the installing step.
 17. A window assembly for use in a subterranean well, the window assembly comprising: a generally tubular housing having a first window formed through a sidewall of the housing; a closure device having a second window formed through a wall of the closure device; and a swellable seal material which prevents fluid transfer between the first and second windows.
 18. The window assembly of claim 17, wherein the closure device is generally tubular in shape and is received within an interior of the housing.
 19. The window assembly of claim 17, wherein the seal material is swollen prior to installation of the window assembly in a wellbore.
 20. The window assembly of claim 17, wherein the second window is displaceable into alignment with the first window, thereby permitting drilling of a lateral wellbore through the aligned first and second windows. 